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5-2
Overview of Explicit Message Communications
Section 5-1
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5-1 Overview of Explicit Message Communications
5-1-1 Explicit Message Communications
Explicit message communications is a communications protocol for sending
commands from the master as explicit messages, and receiving explicit mes-
sages as responses from the nodes that receive the commands.
Explicit messages can be sent from the master to the Digital Controller to read
and write the E5AR/E5ER Digital Controller variable area, send operation
commands, and read and write various other DeviceNet functions supported
by the Digital Controller.
Explicit message communications can be used to send and receive data that
is not allocated in the IN and OUT Areas due to word size restrictions, and
data that does not require the frequent refreshing used by the IN Area and
OUT Area.
Use either of the following two methods depending on the application.
Reading/Writing E5AR/E5ER Variable Area Data and Sending Operation Commands
Send CompoWay/F communications commands to E5AR/E5ER Digital Con-
trollers by embedding them in explicit messages.
Reading/Writing E5AR/E5ER-DRT Maintenance Information
Send explicit messages specific to the DeviceNet-compatible Digital Control-
ler.
5-1-2 Explicit Message Types
The explicit messages sent to the Digital Controller can be divided into two
types: messages in which CompoWay/F commands are embedded and mes-
sages specific to DeviceNet-compatible Digital Controllers.
Sending CompoWay/F Commands to the E5AR/E5ER-DRT (Embedded in Explicit Messages)
The master can send CompoWay/F communications commands to the E5AR/
E5ER Digital Controller by sending them as explicit message data.
When DeviceNet-compatible Digital Controllers are used, the explicit mes-
sages are automatically converted to CompoWay/F communications com-
mands and sent to the E5AR/E5ER-DRT Digital Controller. The responses
from the Digital Controller are converted into explicit messages and returned
to the master. CompoWay/F commands are used to read from and write to the
E5AR/E5ER variable area and to execute operation commands.
CompoWay/F commands consist of binary commands and ASCII commands.
DeviceNet Master
CPU Unit
E5AR/E5ER-DRT Digital Controller
IOWR or
CMND
instruction
Explicit message sent to
DeviceNet-compatible
Digital Controller
CompoWay/F communications
command sent to E5AR/E5ER
Digital Controller (embedded in
explicit message)